The present invention relates to a method of manufacturing liquid cleaning or detergent compositions, which separate into at least two aqueous phases in the rest condition.
One problem which often occurs, both when cleaning hard surfaces, in particular in the kitchen or bathroom area, and when washing soiled fabrics, is that inorganic as well as organic dirt has to be removed. Whereas surface-active agents are usually used to remove organic dirt, they are normally less effective, and in many cases even totally ineffective, when it comes to removing inorganic dirt. In order to remove inorganic dirt, it is therefore necessary to use compounds, generally in aqueous solution, which are suitable for dissolving or detaching this dirt. Depending on the nature of the dirt, these might be acid, neutral or alkaline compounds.
In order to detach deposits of lime scale, which are usually attributable to hardness-forming elements in water, it is preferable to use acid aqueous solutions. In order to remove other types of organic dirt, for example dirt containing clay and/or pigment, it is preferable to use aqueous solutions of ingredients which produce a pH value in the neutral or alkaline range in aqueous solution. In both cases, however, it has been found that the addition of surface-active agents to aqueous solutions used for removing inorganic dirt (if they are also required to remove organic dirt) can lead to a significant reduction in their effectiveness against inorganic dirt.
In German patent application 198 49 247.2, filed by the present applicant, a liquid cleaning or detergent composition which separates into at least two aqueous phases in the rest condition is proposed as a means of resolving this problem. A composition of this type leads to an unexpected improvement in the cleaning effect and, in particular, exhibits a dual action against both organic and inorganic dirt. If such a composition is shaken or mixed before or during use, a dispersion is produced which enables homogeneous application on the surface or substrate. Both on the surface or substrate and in the supply container, this dispersion separates again relatively quickly if left to stand, forming two separate aqueous phases.
The fact that these products consist of at least two liquid phases in equilibrium in the rest condition causes particular difficulties during the manufacturing process. If the products are produced in batches in a liquid mixer, all processes following mixing (such as transportation, storage, packaging, etc.) must be carried out with the mixed product which—by definition—has a tendency to assume the state of equilibrium in which the aqueous phases separate in each rest phase. This being the case, it is difficult to ensure that the relative quantity of each of the several, preferably two, phases remains constant over time.
To do this, it would be necessary, throughout the entire production process, i.e. even during transportation, storage, packaging, etc., to provide for continuous mixing to ensure homogeneity of the product, which will only be effective if the separate aqueous phases of the packaged end product are in the correct predetermined ratio by volume, as desired.
This solution would bring with it specific complications and restrictions in terms of the equipment needed. Conventional filling devices, e.g., metering by means of volumetric cylinders, would be unsuitable. However, even if all equipment components could be set up to meet the requirement of providing continuous mixing, the residence times in the plant would prove to be particularly problematic, since any volumes of product remaining in the system (conduits, filling system, etc.) during these residence periods would undergo the same phase separation desired in the end product.
Even the alternative of separately formulating and packaging the several, preferably two, phases, so that the multi-phase product is not obtained until this stage, provides no satisfactory solution to the problem described above, because each of the two phases is at the equilibrium point, and therefore any slight change, for example in temperature, pressure, etc., could influence the equilibrium, such that multi-phase intermediate products would arise, in which the same processing difficulties would present themselves as those outlined above.